This specification relates to cloud computing.
In cloud computing, data can be distributed to a system of multiple computers connected by one or more communications networks. Each computer can host one or more servers, each of which processes a portion of data. The servers can process the data in parallel. Such a distributed system can handle web-oriented and data-intensive applications deployed in a virtualized environment. For example, a distributed system can be configured to host a multi-tenant computing service over the Internet. A software-as-a-service (SaaS) provider, for example, can run an instance of its application on the distributed system and provide access to multiple tenants.